Institut Curie, Paris Sciences Lettres Research University, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 144, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 144, Paris, France; Cell and Tissue Imaging Core Facility PICT-IBiSA, Institut Curie, Paris, France.
L'Oréal Research and Innovation, Aulnay sous Bois, France.
J Invest Dermatol. 2018 Mar;138(3):647-656. doi: 10.1016/j.jid.2017.09.039. Epub 2017 Oct 18.
The melanosome pattern was characterized systematically in keratinocytes in situ in highly, moderately, and lightly pigmented human skin, classified according to the individual typological angle, a colorimetric measure of skin color phenotype. Electron microscopy of skin samples showed qualitatively and quantitatively that in highly pigmented skin, although melanosomes are mostly isolated and distributed throughout the entire epidermis, clusters are also observed in the basal layer. In moderately and lightly pigmented skin, melanosomes are concentrated in the first layer of the epidermis, isolated-but for most of them, grouped as clusters of melanocores delimited by a single membrane. Electron tomography resolving intracellular three-dimensional organization of organelles showed that clustered melanocores depict contacts with other cellular compartments, such as endoplasmic reticulum and mitochondria. Additionally, immunogold labelling showed that clusters of melanocores do not correspond to autophagosomes or melanophagosomes but that they present, similarly to melanosomes in melanocytes, features of nonacidic, nondegradative organelles. Overall, these observations suggest that melanocore clusters do not correspond to autophagic organelles but represent reservoirs or protective structures for melanosome integrity and function. These results open avenues for understanding the basis of skin pigmentation in different skin color phenotypes.
黑色素体模式在根据个体类型角分类的高度、中度和轻度色素沉着的人类皮肤原位角质形成细胞中进行了系统表征，这是肤色表型的比色测量。皮肤样本的电子显微镜检查定性和定量地表明，在高度色素沉着的皮肤中，尽管黑色素体大多是孤立的并分布在整个表皮中，但在基底层也观察到了簇状。在中度和轻度色素沉着的皮肤中，黑色素体集中在表皮的第一层，孤立的-但对于大多数黑色素体来说，它们被成群结队地聚集在一起，由单个膜界定的黑素核心簇。解析细胞器细胞内三维组织的电子断层扫描显示，聚集的黑素核心与其他细胞区室（如内质网和线粒体）接触。此外，免疫金标记显示，黑素核心簇与自噬体或噬黑素体不对应，而是与黑素细胞中的黑色素体一样，具有非酸性、非降解细胞器的特征。总的来说，这些观察结果表明，黑素核心簇不对应于自噬细胞器，而是代表黑色素体完整性和功能的储库或保护结构。这些结果为理解不同肤色表型的皮肤色素沉着的基础开辟了途径。
